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Logic Gates/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim is walking down a sidewalk in a suburban neighborhood. He is wearing a backpack and singing to himself. TIM: Um-um, coming home from school. Um-um, gonna jump in the pool. Bamp, bamp, bamp! He reaches his front door, abruptly stops singing, and looks down. TIM: Oh. Hey. A small robot is standing on his welcome mat, which reads Beware of Droid. TIM: Can I? He attempts to get past the droid and open his door. The droid blocks his way. TIM: No. He attempts to get past the droid a second time. The droid blocks his way again. TIM: Moby! Moby peeks out through the front door's letter slot. MOBY: Beep. TIM: An AND-droid? Moby hits a button on a remote control that he is holding. The number 1 appears on three little screens attached to the droid and the droid moves aside. Tim opens the front door and enters his house. TIM: What's with that guy? MOBY: Beep. Moby hands Tim a sheet of paper. Tim reads from a typed letter. TIM: Dear Tim and Moby, why does my phone get hot when I have a lot of apps running? From, Sylvie. Hey, Sylvie. If you've ever opened up an electronic device, you probably saw one of these. Tim holds up a circuit board. TIM: This is a circuit board. It holds the main parts of a circuit, and controls the flow of electricity to them. An image shows a circuit board. TIM: Close up, you'll see something like little pathways. In fact, that's just what they are, paths for electricity to flow from one piece to another. An animation shows a small part of the circuit board with a variety of pathways. Animated electrical charges move along the paths and light up different nodes. MOBY: Beep. TIM: Right, as electricity streams through the circuit, it's also passing along tiny pieces of information. The current is actually pulsing in a kind of code called binary. The electrical charges on the circuit board change to look like dots of different sizes to symbolize binary pulses. MOBY: Beep. TIM: Yup, binary is usually represented as 1s and 0s. These values are known as bits, but they don't have to be numbers. You can make a binary code out of any unmatched pair. An animation of 1s and 0s fills the screen. TIM: Braille is a special kind of binary where the bits are raised dots and blank spaces. An animation shows the Braille alphabet, with fingertips moving across it. TIM: In Morse code, the bits are long and short pulses of sound or light. An animation shows a ship at sea. It is night, and a light on the ship flashes Morse code. TIM: And in digital circuits, the bits are a low voltage and a higher voltage. In other words, computers and other electronic devices think in a binary code made of electricity! An animation shows two short pathways on a circuit board. One pathway is labeled with a 0. The other pathway is labeled with a 1. Low-voltage electricity flows along the 0 pathway, and higher voltage electricity flows along the 1 pathway. TIM: To process the code, they rely on something called a logic gate. MOBY: Beep. TIM: A logic gate is sort of like an electric switch. Binary bits of electricity flow into it through one or more inputs. An animation shows the AND- droid from earlier in the film. The droid's two legs become electrified, to illustrate binary input. TIM: Depending on the value of those bits, the gate will send a 0 or a 1 as an output. A little screen on the AND-droid's head shows a 0 and then a 1, to demonstrate the outputs Tim describes. TIM: Our little friend here works like an AND gate. His output voltage will only be high when both inputs are high. If one or both inputs are low, the output will be low. An animation of the AND-droid shows it receiving two high voltage inputs, with a binary value of 1. It's output is also high voltage, with a binary value of 1. Other animations illustrate that when one or both of the inputs is 0 the output will also be 0, or low voltage. TIM: We can view these combinations in a truth table. See? The output is 0 unless both inputs receive a 1. A truth table with columns labeled Input and Output shows columns of 1s and 0s. Input of two 0s makes an output of 0. Input of 0 and 1 makes an output of 0. Input of 1 and 0 makes an output of 0. Input of two 1s makes an output of 1. The row showing the output of one flashes as Tim describes it. AND-DROID: Bloorp! The AND-droid jumps up and down. MOBY: Beep. Moby points at something. TIM: Right, the house alarm is a good example. Tim walks to an alarm panel on the living room wall. TIM: The siren will only sound if it receives a 1 from this AND gate. One of the gate's inputs connects to the keypad. Pressing on sends a 1 to that input; otherwise, it gets a 0. A motion detector connects to the other input. It sends out a 1 if something inside the house moves. So if the system is on and something moves, the AND gate gets two 1s. That means it outputs a 1, and the siren goes off. An animation a little AND-droid acting as the logic gate for the panel. The inputs of the motion detector and on button lead to the output of the siren as Tim describes. MOBY: Beep. TIM: Oh, right, the back door! There's a motion detector there, too. An animation shows the AND-droid, with inputs labeled as front door and keypad, and the output labeled as siren. A label for the back door appears, but does not does not fit anywhere on the AND-droid. TIM: That means we have to add an OR gate to the circuit. Now, if one or both detectors gets tripped, a 1 will be sent to the AND gate. And if the system is on, the siren will sound. A second droid appears, representing an OR gate. The OR-droid connects to the AND-droids leg that used to get input from the front door. The OR-droids two legs are now labeled to accept input from both the front door and the back door. A truth table appears onscreen for the OR gate. For the OR gate, two 0 inputs makes a 0 output, but any combination of 1s and 0s, or all 1s, makes a 1 output. The OR-droid receives an electric signal with an input of 1 from its front door leg. The OR-droid then sends a 1, to AND-droid. Both of the AND-droids inputs are now 1, so its output becomes 1 and the siren goes off. MOBY: Beep. TIM: I was just getting to the windows. Each one has a NOT gate attached to it. An animation of two windows shows a NOT gate droid on each one. The truth table shows that a 0 input makes a 1 output, and a 1 input makes a 0 output. NOT-DROIDS: Not. TIM: When a window is closed, it sends a 1 through the gate. The NOT gate reverses that to a 0, and the alarm won't sound. If a window is opened, it sends a 0 to the gate. The NOT gate changes that to a 1, and if the system is on, the siren sounds. An animation shows how the NOT-droids become another source of input for the AND-droid. A truth table shows the process Tim describes. MOBY: Beep. TIM: Yeah, once you start stacking gates together, they can make some pretty smart decisions. And this circuit is still really basic; it has one purpose and only uses the simplest three gates. MOBY: Beep. AND-DROID Bloorp! OR-DROID Beep! NOT-DROID Not! TIM: All right, bring out their friends! Moby's chest opens. Four tiny droids emerge representing other types of logic gates. They move around, making various electronic sounds. TIM: There are four other basic gates, each with its own specific truth table. The NAND-gate: when she gets too much juice, she shuts down. The NOR-gate: this guy likes 0s, simple as that. The X-OR-gate: when she gets different inputs, she's a happy camper. And the X-NOR gate: he's matchy. He likes it when his inputs are the same. Energetic rock music plays. Labeled animations of droids and truth tables appear as Tim describes each one. They all land in a group with the other droids. TIM: Computers have millions and millions of these gates packed inside them. MOBY: Beep. TIM: They're clustered inside a computer's microprocessor, the part that manages all your apps and programs. The gates here are specially arranged so that they can process information from lots of different programs. An animation shows a closed circuit and then the internal workings of a microprocessor. TIM: So whether you're finding your position on a map or spinning tiles before they fall, the circuitry is always doing the exact same thing. The only difference is in how each program uses it! An animation shows a smartphone. A GPS screen displays, followed by a game screen. MOBY: Beep. Moby reminds Tim of the letter he read at the beginning of the film. TIM: Oh, right: those millions of gates are why your phone can get hot. The more apps you're using, the more bits the gates are processing. That's millions of electric pulses per second, and they throw off some heat! An image shows electrical currents pulsing through a microprocessor. MOBY: Beep. Moby looks sadly down at his opened chest, where the droid logic gates are beeping weakly. TIM: Aww. Poor little guys. Tim examines Moby's interior, where the droids are hot and exhausted. Tim switches on a handheld fan and aims it into Moby's chest to cool off the droids. VOICE-OVER: Gate is Enough was filmed before a live studio audience. The image fades, and closing credits run. An image shows a family of droids playing in a living room. One is riding on the back of a horse. Peppy theme music plays. Images show droids covered with suds in a laundry room, droids standing in a city street, droids sitting around Bill Clinton as he reads to them, and droids having a picnic in the park. Category:BrainPOP Transcripts Category:BrainPOP Engineering & Technology Transcripts Category:BrainPOP Math Transcripts